Users Manual NeuroLog™ System
NL100AK - Headstage
NL100AK
The NL100AK is supplied with several fittings and accessories.
1) A 6.35mm diameter (0.25") metal mounting rod which fits into the hole at the rear of the NL100AK, next to the output cable, and is secured by a small grub screw. This rod can be used to secure the
NL100AK to a micro-manipulator or clamp etc.
2)
3)
Three input cables are supplied two with a stackable 1mm pin connector each and one with a short
U-shaped link (see below for application).
A 1mm stacking plug and a 2mm pin. These are used to make connections with microelectrodes, as described below.
Where possible, it is recommended that microelectrodes are attached directly to the NL100AK input so that the lead length between the NL100AK input and the electrode is minimised; even a few centimetres of lead may result in substantial mains interference (pick-up).
When using fluid filled pipette electrodes it is recommended that an electrode chamber (part no: NL101) is used.
Digitimer Ltd
E-mail: sales@digitimer.com
Page 1 of 2
Tel: +44 (0)1707 328347; Fax: ...373153
Copyright © 1995-9
Website: www.digitimer.com2

Users Manual
NeuroLog™ System NL100AK
Metal microelectrodes may be connected by using an electrode holder (part no: NL04). Alternatively the user can adapt the 2mm connector (supplied) to suit the particular electrode used. A common solution is to use a short length (5-10mm) of hypodermic needle tubing soldered to the pin (keep this connection as short as possible for low interference).
When the NL100AK HEADSTAGE is used in conjunction with the NL104A AC PREAMPLIFIER it is important that the "A-B" position is selected on the NL104A input selector switch. This will reduce interference from external sources and match offset components inherent to the low noise, high input impedance stage in the
NL100AK.
Single ended recordings can be accomplished by grounding the "B" input of the NL100AK with the input cable having the "U" shaped 1mm jumper (supplied); the "U" shaped plug is pushed into the "B" and "GND" inputs and the flying lead is used to provide the ONLY ground connection for the preparation. (See catalogue application note entitled 'Avoiding Ground Loops'). In this way any common-mode interference picked up at both the "A" and "B" inputs of the NL100AK can be summed out by the NL104A.
A DC path must be provided from each input of the NL100AK to the system ground. This DC path may of course be through a high resistance microelectrode. It is also essential, for the best noise performance, to make the ground connection to the biological preparation through the GND terminal of the NL100AK. If the
NL100AK is used differentially, with both A and B inputs connected through electrodes to the preparation, a connection to the NL100AK GND should still be made to the preparation.
Although the NL100AK Headstage is most frequently used with high resistance microelectrodes, its very low noise allows it to be used with low resistance electrodes (eg for differential recordings of action potential through gross electrodes).
WARNING - It should be pointed out that if the input device of, or cable to, the Headstage should fail there is a possibility of current flowing though the preparation to ground causing an inadvertent lesion 1 . This is limited by the design to approximately 650
µ
A. Should this be a problem (and it is a remote possibility) please contact
Digitimer for advice.
ALSO - make certain that the NL900 power switch is on before connecting the preparation to the active inputs of the NL100AK (or NL104A). Do NOT switch the NL900A power on or off while a preparation is connected to the NeuroLog™ System.
Do NOT attempt to use oversize plugs with the headstage sockets, as pins greater then 1.00/2.00mm diameter will damage the socket.
NOTE: if the NL100AK is required to plug into the NL103 amplifier which is fitted with an input socket without locating keyway, the NL100A (first stage) should be ordered to ensure that the correct mating plug is fitted to the connecting cable.
(1) - Recording of Brain Potentials with FET-Circuits: Hazard of Inadvertent Lesions, by J. A. W. M. Weijnen and N. Chedhade in Brain Research Bulletin , Vol. 18 , pp617-618.
Input resistance
Gain
Input noise
10 8 ohms
:+1.0
:<2
µ
V (peak to peak) with inputs shorted
<25
µ
V for a typical tungsten microelectrode in saline
<30
µ
V with a 1 Megohm resistor between inputs
(bandwidth in all three cases, 10Hz to 10kHz)
First Issued: - before July 1984 Last Revision: - January 12, 1999
File Reference: - N:\DOCS\COMPANY\MANUALS\NEUROLOG \ NL100AK.SAM
Printed: - January 12, 1999
Digitimer Ltd
E-mail: sales@digitimer.com
Page 2 of 2
Tel: +44 (0)1707 328347; Fax: ...373153
Copyright © 1995-9
Website: www.digitimer.com2